Serving multi-turn agent workflows on standard LLM inference engines quickly degenerates into an input-bound memory bandwidth nightmare. When an agent loops through tool executions and reasoning traces, repeatedly processing identical prompt prefixes wastes massive compute and saturates GPU memory bandwidth.
SGLang tackles this through RadixAttention, a mechanism that maintains an LRU cache of key-value states inside a radix tree across independent requests. Instead of discarding the KV cache after generation or forcing linear caching, the runtime matches incoming prompt token prefixes directly against the tree hierarchy.
This architecture enables seamless prefix sharing across branching agent trajectories, few-shot prompts, and speculative decoding paths. By retaining memory pages on device and swapping them via an eviction policy, cache hit rates regularly exceed eighty percent in production agent setups.
High-throughput LLM serving is no longer just about raw tensor parallelism; it is fundamentally an operating system problem of memory page reuse and scheduling.













